Restrict inlining of local fun references

Local fun references look like plain old variables in the Core Erlang
AST but should not be treated as such. Inlining of such expressions is
now restricted to application contexts as a local fun reference should
never occur in a guard.

This is not perfect as it forbids inlining in some safe situations, but
that is still better than a compiler crash.

1 files changed, 30 insertions, 9 deletions

diff --git a/lib/compiler/src/cerl_inline.erl b/lib/compiler/src/cerl_inline.erl
index 2e7554c1ff..c6de63c69f 100644
--- a/lib/compiler/src/cerl_inline.erl
+++ b/lib/compiler/src/cerl_inline.erl
@@ -52,7 +52,7 @@
 	       clause_pats/1, clause_vars/1, concrete/1, cons_hd/1,
 	       cons_tl/1, data_arity/1, data_es/1, data_type/1,
 	       fun_body/1, fun_vars/1, get_ann/1, int_val/1,
-	       is_c_atom/1, is_c_cons/1, is_c_fun/1, is_c_int/1,
+	       is_c_atom/1, is_c_cons/1, is_c_fname/1, is_c_int/1,
 	       is_c_list/1, is_c_seq/1, is_c_tuple/1, is_c_var/1,
 	       is_data/1, is_literal/1, is_literal_term/1, let_arg/1,
 	       let_body/1, let_vars/1, letrec_body/1, letrec_defs/1,
@@ -1578,7 +1578,7 @@ make_let_binding_1(R, E, S) ->
 %%  completely.
 
 copy(R, Opnd, E, Ctxt, Env, S) ->
-    case is_c_var(E) of
+    case is_c_var(E) andalso not is_c_fname(E) of
         true ->
 	    %% The operand reduces to another variable - get its
 	    %% ref-structure and attempt to propagate further.
@@ -1628,12 +1628,12 @@ copy_var(R, Ctxt, Env, S) ->
     end.
 
 copy_1(R, Opnd, E, Ctxt, Env, S) ->
-    %% Fun-expression (lambdas) are a bit special; they are copyable,
-    %% but should preferably not be duplicated, so they should not be
-    %% copy propagated except into application contexts, where they can
-    %% be inlined.
-    case is_c_fun(E) of
-        true ->
+    case type(E) of
+        'fun' ->
+            %% Fun-expression (lambdas) are a bit special; they are copyable,
+            %% but should preferably not be duplicated, so they should not be
+            %% copy propagated except into application contexts, where they can
+            %% be inlined.
             case Ctxt of
                 #app{} ->
                     %% First test if the operand is "outer-pending"; if
@@ -1649,7 +1649,28 @@ copy_1(R, Opnd, E, Ctxt, Env, S) ->
                 _ ->
                     residualize_var(R, S)
             end;
-        false ->
+        var ->
+            %% Variables at this point only refer to local functions; they are
+            %% copyable but can't appear in guards, so they should not be
+            %% copy propagated except into application contexts, where they can
+            %% be inlined.
+            case Ctxt of
+                #app{} ->
+                    %% First test if the operand is "outer-pending"; if
+                    %% so, don't inline.
+                    case st__test_outer_pending(Opnd#opnd.loc, S) of
+                        false ->
+                            R1 = env__get(var_name(E), Opnd#opnd.env),
+                            copy_var(R1, Ctxt, Env, S);
+                        true ->
+                            %% Cyclic reference forced inlining to stop
+                            %% (avoiding infinite unfolding).
+                            residualize_var(R, S)
+                    end;
+                _ ->
+                    residualize_var(R, S)
+            end;
+        _ ->
             %% We have no other cases to handle here
             residualize_var(R, S)
     end.